The present invention relates to a prosthetic system for joint replacement, and more particularly to a trial fixation device for securing a trial in the medullary canal of a resected bone so that accurate measurements can be made for fitting a prosthetic implant.
Patients suffering from trauma or disorders causing severe joint pain often require surgical treatment involving complete or partial replacement of the affected joint. For example, prostheses for replacing all or a portion of a damaged or diseased knee, hip, and shoulder of a person are well known.
When reconstructing damaged or diseased joints with an artificial prosthesis, it is desirable to position the components of the prosthesis such that the structure and function of the properly functioning natural joint is replicated to the greatest degree possible. This involves consideration of several factors. For example, the components of the prosthesis must be inserted such that the patient has the desired limb length after surgery. It is also desirable that the range of motion of the joint after surgery is, to the extent possible, the same as that of a healthy joint. Some of the factors relevant to proper placement include insertion depth of the prosthesis components into the bone and rotational orientation of the prosthesis components.
During a shoulder replacement operation, at least a portion of the proximal section of the humeral shaft is replaced by a metal prosthesis. This prosthesis generally consists of two parts: a stem that is mounted into the medullary canal of the humerus, and a head component connected in some manner to the stem. The head component replaces the bearing surface of the humerus and articulates within the glenoid cavity of the scapula to allow movement of the shoulder. An example of a humeral prosthetic system is the Neer 3 System from Smith and Nephew, Inc.
The stem and head component of a humeral prosthesis may be supplied in xe2x80x9cmodularxe2x80x9d form, that is, as separate connectable components. Different stem sizes and head sizes in a modular implant design provide the surgeon with some degree of flexibility, which facilitates reconstruction of the original anatomy of the patient.
With a range of stem sizes and a range of head sizes available, the surgeon can choose a particular combination to suit the anatomy of each individual patient without having a large inventory of xe2x80x9cintegralxe2x80x9d or xe2x80x9cmonoblockxe2x80x9d humeral prostheses. For example, one patient may require a relatively small head and a relatively long stem. With a monoblock prosthesis, a wide range of stem lengths and/or diameters are required for each head size, whereas with a modular arrangement, a particular head may be used with a range of stem, sizes, and a particular stem may be used with a variety of head sizes.
Additional variations also arise because individual patients may require differing angles of inclination of the head relative to the stem and differing eccentricities between the axis of the head and the axis of the stem. Thus, for example, in one patient, the eccentricity may be posterior and in another patient, it may be anterior.
Various shoulder prostheses are disclosed in European Patent Publication No. EP-A 0 679 375; EP-A 0 712 617; French Patent No. FR-A 2 664 809; U.S. Pat. Nos. 3,694,820; 3,803,641; 4,045,825; 4,106,130; 4,179,758; 4,865,605; 4,919,670; 5,358,526; 5,549,682; 5,462,563 and 5,702,457; and PCT International Patent Publication No. WO 96/17553, the entirety of which are hereby incorporated by reference.
Before surgery to reconstruct a patient""s shoulder with a humeral prosthesis, x-rays and x-ray templates are used to give an indication of the necessary height and size of the prosthesis. During surgery trial stems and heads are used by the surgeon to choose the appropriate offset height and retroversion for the humeral prosthesis. The trial stem is inserted into the medullary canal, the trial head is attached (in the case of a modular trial), and the shoulder is taken through a range of motion. The trial stem may be graduated at 5 mm intervals to facilitate the determination of the proper height for stem implantation. Typically, an alignment rod is used to check retroversion.
The trial implant position is critical for restoring the height of the humerus and the degree of retroversion. The height of the humerus effects the balance of the soft tissues. The soft tissues are attached to the prosthesis in a balanced manner to avoid subluxation and for a good range of motion. If the offset is too high, then the soft tissue tension is too tight and if the offset is too low, then the soft tissue tension is too lax.
In order to accurately test the correct height of the trial stem, the trial stem is held in place in the medullary canal. Current methods of securing the trial stem in the medullary canal include packing gauze in the medullary canal around the trial stem to keep it in position. This method does not allow the surgeon an easy way to adjust the height, if the trial stem is found to be at the incorrect height, or provide a reliable method of keeping the trial stem in place during the range of motion test.
Another method is to use an extramedullary device to hold the trial stem in place. These extramedullary devices are big and bulky and prevent an effective range of motion being investigated during surgery and do not allow the surgeon to close the tuberosities and other soft tissue around the trial stem in order to check the balance of soft tissues.
Methods, devices, and systems of this invention seek to provide a trial fixation device for use in complete or partial joint replacement and repair that secures a trial in the medullary canal of a bone. With the trial fixation device of the invention, the trial can be securely fixed in the bone canal, the trial can be put through a full range of motion, the balance of the soft tissues can be tested, and the height of the trial can easily be adjusted if necessary.
Methods, devices, and systems according to this invention more particularly provide an intramedullary trial fixation device designed to engage a trial and secure the trial in the canal of a bone, a prosthetic system for replacement or repair of all or a portion of the damaged joint, and methods for using the intramedullary trial fixation device to replace or repair a damaged joint. In one embodiment, the primary components of the trial fixation device are a body adapted to be received in the resected bone and adapted to receive a trial stem and a fixation portion attached to the body for engaging the trial stem.
An additional aspect of this invention is a surgical system that includes a selection of prosthetic implants of various sizes and shapes, a corresponding selection of trial prostheses, a corresponding selection of fixation devices, and a selection of devices for implanting and removing the fixation device.
Another aspect of this invention seeks to provide a method of using the trial fixation device for replacing or repairing all or a portion of a damaged joint and orienting the prosthesis to compliment the patient""s natural anatomy. More particularly, this invention provides a method of replacing the proximal humerus and humeral head.
These and other features of this invention will become apparent after a review of the following detailed description of the disclosed embodiments.